Flowering plants survived the asteroid that killed the dinosaurs – and may outlive us
If you somehow survived the initial impact, you would have witnessed the devastation that followed. Raging firestorms, mega tsunamis, and… Nuclear winter Lasting months to years. The 180-million-year era of the non-avian dinosaurs ended in the blink of an eye, and so did at least 75% of species Who shared the planet with them.
After this event known as Mass extinctions in the Cretaceous and Paleogene (K-Pg), a new dawn has appeared for Earth. The ecosystems had revived again, but the life that inhabited them was different.
Many famous pre-K-Pg types can only be seen in the museum. The massive one Tyrannosaurus rexthe Velociraptorand winged dragons Quetzalcoatlus The race was unable to survive the asteroid and is confined to deep history. But if you take a walk outside and smell the roses, you will be in the presence of ancient lineages that flourished in the ashes of K-Pg.
Although the living species of roses are not the same as the ones I shared the land with Tyrannosaurus rexTheir lineage (Wardia family) It arose tens of millions of years ago Before the asteroid hit.
Roses are not an unusual breed of angiosperms (flowering plants) in this regard. Fossils and genetic analysis indicate that The vast majority of families are angiosperms Originated before the asteroid.
The ancestors of the ornamental orchid families, the magnolia and passionflower families, the grass and potato families, the medicinal daisy family, and the herbaceous mint family, all shared the land with dinosaurs. In fact, the massive evolution of angiosperms to approximately 290,000 species today may have been facilitated by K-Pg.
Like the early members of our lineage, angiosperms seem to have benefited from a fresh start. Mammals.
(PopTika/Shutterstock) Flowers are surprisingly resilient.
However, it is not clear how they did this. Angiosperms, which are extremely fragile compared to dinosaurs, cannot fly or run to escape harsh conditions. They depend on sunlight for their existence, which has been erased.
What do we know?
Fossils found in different areas tell different accounts of the events. Clearly there has been a high rate of angiosperm turnover (loss and reemergence of species) On Amazon When the asteroid hit, the numbers of plant-eating insects declined In North America Which indicates the loss of food plants. But other areas Like Patagoniadoes not show any pattern.
A study conducted in 2015 analyzed 257 angiosperm fossils Genres (Families usually contain multiple genera) K-Pg has been found in Little effect On extinction rates. But it is difficult to generalize this result across 13,000 angiosperm genera.
My colleague Santiago Ramírez Barahona, from the National Autonomous University of Mexico, and I took a new approach to resolve this confusion in a study we conducted Recently published In Biology Letters. We analyzed large angiosperm family trees, which previous work had drawn through mutations in the DNA sequences of 33,000 to 73,000 species.
This way of tree thinking has laid the foundation for major insights into the evolution of life since Charles Darwin wrote the first family tree.
Charles Darwin’s first diagram of an evolutionary tree from 1837
Although the family trees we analyzed did not include extinct species, their shape contains clues about how extinction rates change over time, through the way the rate of branching ebbs and flows.
The rate of extinction of a lineage, in this case angiosperms, can be estimated using mathematical models. The method we used compared the age of the ancestor with estimates of how many species should appear in the family tree according to what we know about evolution.
It also compared the number of species in a family tree with estimates of how long it takes for a new species to evolve. This gives us the net diversification rate – how quickly new species appear, adjusted for the number of species that have disappeared from the lineage.
The model creates time scales, such as million years, to show how the extinction rate varies over time. The model allowed us to identify time periods that witnessed high extinction rates. It can also refer to times when there have been major shifts in species creation and diversification, as well as when there has been a mass extinction event. It shows how much DNA evidence supports these findings as well.
We found that extinction rates appear to be remarkably constant over the past 140-240 million years. This discovery highlights how resilient angiosperms have been over hundreds of millions of years.
We cannot ignore Fossil evidence It shows that many angiosperm species have already disappeared around K-Pg, with some sites more damaged than others. But as our study confirms, the lineages (families and orders) to which species belong persisted undisturbed, creating life on Earth as we know it.
This is different from the case of non-avian dinosaurs, which disappeared completely: their branch was completely pruned.
Scientists believe Flexibility of angiosperms The K-Pg mass extinction (why only the leaves and branches of the angiosperm tree were pruned) can be explained by their ability to adapt. For example, their development of new mechanisms for seed dispersal and pollination.
They can too Replication of the entire genome (all the DNA instructions in an organism) which provide a second copy of each gene on which selection can act, potentially leading to new forms and greater diversity.
The sixth mass extinction event We are currently facing You may follow a similar path. An alarming number of angiosperm species are already threatened with extinction, and their demise will likely spell the end of life as we know it.
It is true that angiosperms may flourish again from a diverse group of survivors – and may outlive us.
Jamie Thompson is a postdoctoral biologist at the University of Bath. This article was republished from Conversation under Creative Commons license. Read the Original article.